1. Field of the Invention
The present invention relates to a ferrite-containing plastic composition useful for forming anti-noise parts which are used for removing noises for various electronic appliances. The present invention also relates to a deflection yoke made of such a composition, particularly a deflection yoke useful for an image receiving tube which can be used for televisions or display monitors.
2. Discussion of Background
FIG. 2 is a perspective view of a conventional ferrite bead useful for removing high frequency noises.
In the Figure, reference numeral 4 designates a ferrite bead formed of a ferrite-containing plastic composition, numeral 2 is a through-hole, and numeral 3 is a lead wire passing through the through-hole 2.
With this structure, the ferrite bead 4 portion has an impedance in a high frequency region and provides a function to absorb and attenuate high frequency noises.
With such a conventional ferrite bead formed of a ferrite-containing plastic composition, the particle size of the ferrite particles contained is small, and the ferrite content is low, whereby the function to absorb and attenuate the high frequency noises is rather limited, and an effective attenuation effect can not be obtained. In order to increase the attenuation effect, the shape is obliged to be enlarged.
However, if the particle size of the ferrite particles is increased too much in order to increase the attenuation effect, the moldability and processability which are characteristic features of the plastic ferrite will be lost.
It is an object of the present invention to overcome such problems and to provide a ferrite-containing plastic composition which is capable of effectively removing high frequency noises and which, at the same time, provides the desired moldability and processability characteristic to a plastic ferrite (a ferrite-containing plastic composition).
With respect to a deflection yoke, an apparatus as illustrated in FIGS. 5 to 7 has been known. In these Figures, reference numeral 11 designates a deflection yoke, numeral 12 indicates an image receiving tube having such a deflection yoke mounted thereon, and numeral 13 is the main body of the deflection yoke 11, which is a sintered ferrite core made of a sintered ferrite material. Numeral 14 indicates a deflecting coil, and numeral 15 indicates a separator. The deflection yoke 11 is constituted by the yoke main body 13, the deflecting coil 14, a substrate (not shown), etc. As shown in FIG. 7, it is used as attached to the neck portion of the image receiving tube 12. Numeral 16 indicates grooves for winding.
The deflecting coil 14 of the image receiving tube 12 comprises two sets of vertical and horizontal coils. When saw tooth currents for vertical and horizontal scanning are conducted thereto, an electron beam will be deflected up and down, and left and right, so that a raster will be depicted on the image receiving tube 12.
The conventional deflection yoke was formed of a sintered ferrite material and tends to undergo shrinkage after the sintering. Accordingly, it was required to improve the processing precision by conducting e.g. milling after sintering in order to improve the precision of e.g. grooves 16 for winding.
Further, with a deflection yoke, the precision of the video image depends largely on the magnetic flux density distribution of the deflecting magnetic field, and the distribution of the deflecting magnetic field is determined by the winding shape and the winding density distribution of the deflecting coils. Accordingly, in order to improve the precision of the video image, it is necessary to provide grooves 16 for winding to improve the winding precision with respect to the yoke body 3 as shown in FIG. 3, and the processing precision is required for forming the grooves 16 for winding. For this reason, it was difficult to produce highly precise deflection yokes in a large quantity, and there was a problem that the production cost tended to be high.
Accordingly, it is another object of the present invention to overcome such problems and to provide an inexpensive deflection yoke having a high deflecting precision using a plastic ferrite comprising a ferrite powder, a plastic and a small amount of additives, by improving the moldability and the processing precision and eliminating the necessity for processing after sintering.